The present invention relates generally to end closures for food and drink containers and more particularly to can end closures which have improved scoring in combination with easy opening features which are environmentally acceptable.
There has been a continuing demand for a lid construction for such containers which may be opened without the need of separate opening devices. One such construction generally termed the "pull-tab", embodies a scored outline in the surface of the container lid and a supplemental pull ring attached to an end of the outline to facilitate tearing along the scored outline and lifting it from the can end. That construction has several inherent disadvantages, one relates to the possibility of minor injuries resulting from contact with the edges of the opening or of the discarded pull-tab. A further disadvantage of such construction relates to ecology, and involves the rather prevalent indifference as to the proper disposal of the detached tabs causing complaints of injury and litter and promoting legislation directed at the banning of such container closures. Similarly, the need to add the pull ring is costly and wasteful of material and energy.
Another type of can end construction which has been proposed in recent years is the push-in tab type. An example of can end construction of this type can be found disclosed in U.S. Pat. No. 4,054,228 granted Oct. 18, 1977 and the other prior art therein cited. Those prior patents disclose can opening arrangements which embody can ends having score lines, partial shearing and severing defining two inwardly-displaceable raised tab portions in the can end. The partial shear or severance leaves a residual wall section which is intended to break when the tab portion is depressed. Some prior art shows closures provided with two openings which are closed by slugs stamped from the end panel and are secured to a peelable strip or tape. None disclose an arrangement which is capable of retaining a vacuum and internal pressure.
The prior patent to Balocca et al (U.S. Pat. No. 4,054,228) is singular in its recognition of the problem of using the aforesaid inwardly displaceable tabs with food and drink which are subject to positive and negative pressure during packing and processing. More particularly, a vacuum results where a hermetic seal is required and generates a vacuum pack having atmospheric pressure greater than the internal pressure of the container. The Balocca et al U.S. patent discloses a two sealant means to reinforce and hold the inwardly displaceable tabs against the force of atmospheric pressure. Such an approach was effective to a degree being limited as to the adhesive application consistency and strength of the sealants and the temperature to which the container could be raised during processing. The flexibility sought with respect to the desired vacuum retention by inwardly displaceable tabs is achieved by the present disclosed scoring, shearing and coining of the inwardly displaceable tabs.
It is, therefore, a primary object of the present invention to provide an improved easy open can end closure with scoring and coining of the tabs to eliminate in whole or in part the disadvantages inherent in the can and closures discussed above. More specifically, it is an object of the invention to provide novel forming of the tabs for a can end closure having facile opening features which are ecologically advantageous.